The present invention relates to an apparatus for detecting a liquid level in a container. In particular, the invention concerns an apparatus for monitoring constantly a liquid level in a transparent container such as a dropper and producing an alarm when the liquid level has attained a predetermined value. Although not exclusive, the invention is particularly applicable to an apparatus for monitoring the liquid level in a dropper in which a liquid containing medicine and nutritive substances are contained and injected continuously and directly into a blood vessel of a patient, thereby to produce an alarm signal when a lower limit of the liquid level is detected.
Heretofore, the monitoring of the liquid level in the dropper of the above kind has relied on the care and attention of an attendant or nurse attending a patient. It is essentially important to replace a fresh dropper container when the liquid level in the dropper container now being used has attained an allowable minimum level. Otherwise, there would arise a danger that air might be injected into the blood vessel of the patient. Thus, heavy burden is imposed on the nurse and attendant for monitoring the liquid level in the dropper container.